WASHINGTON, D.C.— Sanafi al-Nasr, al-Qaeda’s chief financial officer and highest-ranking leader of the Khorasan Group, a terrorist organization intent on attacking America and its allies in the West, was killed in a U.S.-led coalition airstrike in Syria, the Pentagon has announced.

Al-Nasr “worked for al-Qaeda’s Iran-based facilitation network” before assuming charge of al-Qaeda’s core finances in 2012 and then relocating to Syria in 2013 where he had become the Khorasan Group chief, noted Peter Cook, press secretary at the U.S. Department of Defense (DOD), in a statement issued Sunday, announcing the Oct. 15 execution of the group’s chief.

He is now “the fifth senior Khorasan Group leader killed in the last four months,” added Cook.

Members of the Khorasan Group, a network of seasoned al-Qaeda operatives, believed to be mainly from Afghanistan and Pakistan, were the primary targets of the first round of U.S.-led coalition airstrikes in Syria—40-plus Tomahawk cruise missiles—launched in late September 2014.

At the time, the Pentagon explained that United States targeted the group in an effort to thwart an imminent attack against the American homeland, claiming the Khorasan Group “was nearing the execution phase of an attack either in Europe or the homeland.”

“In terms of the Khorasan group, which is a network of seasoned al Qaeda veterans, these strikes were undertaken to disrupt imminent attack plotting against the United States and Western targets,” said the then-Pentagon press secretary, Rear Adm. John Kirby. “These terrorists have established a safe haven in Syria to plan external attacks and test improvised explosive devices and recruit Westerners to conduct operations. The United States took action to protect our interests and to remove their capability to act.”

Sanafi al-Nasr, also known as Adballah Ibrahim al Charekh, was identified by the Pentagon as a Saudi national who served as the highest ranking leader of the Khorasan Group.

He was killed in a U.S. airstrike in northwestern Syria on Oct. 15.

“Al-Nasr was a long-time jihadist experienced in funneling money and fighters for al-Qaeda. He moved funds from donors in the Gulf region into Iraq and then to al-Qaeda leaders from Pakistan to Syria,” stated Pentagon press secretary Cook on Sunday. “He organized and maintained routes for new recruits to travel from Pakistan to Syria through Turkey in addition to helping al-Qaeda’s external operations in the West.”

The former chief financial officer for al-Qaeda had been officially deemed a Specially Designated Global Terrorist by the U.S. Treasury Department.

“The United States will not relent in its mission to degrade, disrupt and destroy al-Qaeda and its remnants,” said Secretary of Defense Ash Carter. “This operation deals a significant blow to the Khorasan Group’s plans to attack the United States and our allies, and once again proves that those who seek to do us harm are not beyond our reach.”

Members of jihadist social media sites widely mourned the execution of the Khorasan leader, referring to him as a martyr, reports CNN.

Al-Nasr had become a leading figure in the al-Nusra Front, an al-Qaeda affiliate in Syria, since moving to Syria in 2013, said CNN terrorism analyst Paul Cruickshank, adding that his death represented a “significant blow to al Qaeda” given that he was one of the jihadist organization’s most senior figures in Syria.

The Pentagon has described the Khorasan Group as an offshoot of al-Nusra.

“He was a highly influential strategist and prolific online propagandist and previously played key operational roles for the terrorist organization in the Afghanistan-Pakistan border region and Iran, including a stint in 2012 as al Qaeda’s chief financial officer,” said Cruickshank, referring to al-Nasr.

“He is believed to have worked to ensure the group remained within al Qaeda’s orbit and is also believed to have worked closely with deceased Khorasan Group leader Muhsin al Fadhli,” he added.

Kuwaiti-born Al-Fadhli was killed in a U.S.-led coalition strike in July. He may be linked to Iran’s role in the al-Qaeda attacks against the U.S. homeland on Sept. 11, 2001.

U.S. director of national intelligence James Clapper was the first American official to publicly acknowledged the existence of the Khorasan, when he said last year that it was operating in Iraq and Syria with a focus on attacking the West.

Khorasan is an ancient name for a region that encompasses large areas of Afghanistan, Pakistan, Iran, and other surrounding countries.

“Jihadists consider the Khorasan to be the area where they will inflict the first defeat against their enemies in the Muslim version of Armageddon. The final battle is to take place in the Levant – Israel, Syria, and Lebanon,” reported The Long War Journal in May 2012.

In January, al-Qaeda rival Islamic State (ISIS/ISIL) announced that it had expanded to Afghanistan and established the “Khorasan province.”